Appendix A—Sample Methodology and Data Reliability

Sample Selection

The sample for this survey consisted of 1,234 organizations, including 900 districts and 334 other entities. These nondistrict entities were primarily community-based social organizations (e.g., Families First, Woodland Center, and First Presbyterian Learning Center), with a few (9) private schools. The districts and other entities serving migrant students were selected from the U.S. Department of Education's 1995-96 Migrant Education Program Universe file. This list contains 4,180 districts and 662 other community-based social organizations serving migrant students in the United States and Puerto Rico. Of these, 1,401 school districts and 170 other entities reported that they provided summer-term projects for migrant students at the time the frame was being developed.

The sample of school districts was selected through stratified sampling procedures with strata defined by metropolitan status (urban, suburban, rural) and size class (district enrollment). Within these strata, districts were sorted by region (Northeast, Southeast, Central, and West) to induce implicit geographic stratification. Under the design, school districts were sampled systematically within strata using a random start.

Districts with an enrollment of 1,499 students or less were sampled at a rate of 1 in 4, districts with an enrollment of 1,500 to 4,999 were sampled at a rate of 1 in 3, and those with an enrollment of 5,000 to 9,999 were sampled at a rate of 1 in 1.5. All districts with an enrollment of 10,000 students or more were included in the sample with certainty.

All of the 170 other entities that offered regular and summer or summer-only projects for migrant students were included in the sample with certainty. In addition, about 500 other entities that did not report offering summer-term projects in 1995-96 were identified. Because some of these organizations might have added a summer project by the time the survey was conducted, a decision was made to include a sample of these organizations; about one-third (or 164 of the 500 organizations) were selected. To the extent that the sampled organizations were found to offer a summer-term project as reported in the questionnaire, they were included in the analysis sample with an appropriate sampling weight.

Respondent and Response Rates

Questionnaires with letters explaining the purpose of the study were sent to the migrant education director in each sampled district and other entity in September 1998. Telephone followup was conducted from mid-September through early December with districts and other entities that did not respond to the initial questionnaire mailing. Of the 900 districts selected for the study, 11 were found to be out of the scope of the study because they were duplicates-the same district listed more than once on the file. This left a total of 889 districts in the sample; 803 of the eligible districts completed questionnaires for an unweighted district response of 90 percent.

Of the 334 other entities initially sampled, 84 were found to be out of the scope of the study. Three were duplicates on the file and the others were either districts or projects run through public school districts or schools, and project data for these entities would have been reported by their districts, which had a chance of selection. A total of 231 of the 250 eligible other entities participated in the study, yielding an unweighted response rate of 92 percent for other entities. The overall unweighted response rate for the survey was 91 percent, and the weighted response rate was 91 percent.

A total of 1,034 organizations, including districts and other entities, participated in the study. Of these respondents, 681 indicated they provided MEP summer-term instruction in 1998. Data reported for the study are therefore based on responses from 681 organizations. These 681 organizations represent the universe of approximately 1,700 organizations in the United States and Puerto Rico that offered MEP summerterm projects in 1998. One district was selected from Puerto Rico. Item nonresponse rates ranged from 0.0 to 6.1 percent, but were under 1.0 percent for most items.

Sampling and Nonsampling Errors

The responses were weighted to produce national estimates (see Table A-1). The weights were designed to adjust for the variable probabilities of selection and differential nonresponse. The findings in this report are estimates based on the sample selected and, consequently, are subject to sampling variability.

The survey estimates are also subject to nonsampling errors that can arise because of nonobservation (nonresponse and noncoverage) errors, errors of reporting, and errors made in data collection. These errors can sometimes bias the data. Nonsampling errors may include such problems as misrecording of responses; incorrect editing, coding, and data entry; differences related to the particular time the survey was conducted; or errors in data preparation. While general sampling theory can be used in part to determine how to estimate the sampling variability of a statistic, nonsampling errors are not easy to measure and, for measurement purposes, usually require that an experiment be conducted as part of the data collection procedures or that data external to the study be used.

To minimize the potential for nonsampling errors, the questionnaire was pretested with respondents like those who completed the survey. During the design of the survey and survey pretest, an effort was made to check for consistency of interpretation of questions and to eliminate ambiguous items. The questionnaire and instructions were extensively reviewed by the National Center for Education Statistics and the Office of Migrant Education, U.S. Department of Education. Manual and machine editing of the questionnaire responses were conducted to check the data for accuracy and consistency, and cases with missing or inconsistent items were recontacted by telephone. Data were keyed with 100 percent verification.

Variances

The standard error is a measure of the variability of estimates due to sampling. It indicates the variability of a sample estimate that would be obtained from all possible samples of a given design and size. Standard errors are used as a measure of the precision expected from a particular sample. If all possible samples were surveyed under similar conditions, intervals of 1.96 standard errors below to 1.96 standard errors above a particular statistic would include the true population parameter being estimated in about 95 percent of the samples. This is a 95 percent confidence interval. For example, the estimated percentage of migrant education projects that forwarded students' records to their next schools is 60 percent, and the estimated standard error is 2.0 percent. The 95 percent confidence interval for the statistic extends from [60 - (2.0 times 1.96)] to [60 + (2.0 times 1.96)], or from 56 to 64 percent. Tables of standard errors for each table and figure in the report are provided in the appendices.

Terms Defined on the Survey Questionnaire

Migrant Education Program (MEP) : a federally funded program designed to meet the special educational needs of migrant students. It is authorized under Title I, Part C of the Elementary and Secondary Education Act of 1966, and reauthorized in 1994.

Migrant Education Program Summer-Term Projects: projects that use MEP funds to provide instructional and/or support services to migrant students during the summer.

Migrant Student: a person below 21 years of age and without a high school diploma who is, or whose parent, spouse, or guardian is, a migratory agricultural worker (including a migratory dairy worker or fisher), and who has changed school districts in the preceding 3 years in order to (a) obtain seasonal employment in agricultural or fishing work or (b) accompany or join a parent, spouse, or guardian who moves to obtain temporary or seasonal employment in agricultural or fishing work. 5

Sample Universe and Analysis Variables

Enrollment size of project - total number of students served by projects. Less than 100 100-250 Over 250

Student population served - grade level of students served.

Elementary-age students only - lowest grade is less than or equal to 6 and highest grade is less than or equal to 8.

Secondary-age students only - lowest grade is 7 through 12.

Students of all ages - lowest grade is less than or equal to 6 and highest grade is 7 through 12.

Metropolitan status - metropolitan status of district as defined in the Common Core of Data (CCD).

Urban - Primarily serves a central city of a Metropolitan Statistical Area (MSA).

Selected states - based on states with the largest concentration of migrant students. California Texas Other - all other states

Background Information

The survey was conducted under contract with Westat, using the Fast response Survey System (FRSS). Westat's Project Director was Elizabeth Farris, the Survey Manager was Sheila Heaviside, and Basmat Parsad was the main author of the report. Bernie Greene was the NCES Project Officer. The data were requested by the Office of Migrant Education, U.S. Department of Education. The following individuals reviewed this report:

For more information about FRSS or the survey, Participation of Migrant Students in Title I Migrant Education Program (MEP) Summer-term Education Projects,contact:

Bernie Greene, Early Childhood, International, and Crosscutting Studies Division National Center for Education Statistics Office of Educational Research and Improvement U.S. Department of Education Email: Bernard_Greene@ed.gov

5As noted in chapter 1, the definition used in this study differs slightly from the official definition, which specifies eligible migrant students as between ages 3 to 21.